Biology subjects

Lassota, A.

Publications and source records attributed to Lassota, A..

3 recordsLinked to original sources

bioRxiv2025

The neurotrophin DNT-2 regulates cell survival and connectivity via the Toll-2 receptor during visual system development of Drosophila

During development, neurons are produced in excess and those that receive trophic support are maintained, whereas excess neurons are eliminated, enabling the establishment of appropriate neural circuits. In vertebrates, neurotrophin ligands promote cell survival during periods of naturally occurring cell death, by signalling through p75 and Trk receptors. In the Drosophila optic lobe, a wave of apoptosis occurs during neural circuit development; however, whether this also involves neurotrophism remains unresolved. Drosophila neurotrophins (DNTs) are encoded by spatzle (spz) paralogue genes and bind Toll receptors instead. Here, we focused on DNT-3 (previously known as spz-3) and DNT-2 (also known as spz-5) to ask whether they underlie neurotrophism in visual system development. We show that DNT-3 (spz-3) and DNT-2 (spz-5) are both expressed in the retina and in medulla neurons, and multiple Tolls are expressed across lamina and medulla neurons. Over-expression of DNT-3 (spz-3) and DNT-2 (spz-5) could rescue natural occurring cell death, whereas their loss of function caused cell death, showing that DNT-3 and DNT-2 can, and are required to, promote cell survival during optic lobe development. Importantly, DNT-2 is expressed in Mi1 neurons and Toll-2 in connecting L1 neurons. We show that DNT-2 functions in concert with Toll-2, as Toll-2 RNAi knock-down prevented the rescue of apoptosis by DNT-2 over-expression and all Toll-2+ neurons were lost in DNT-2 mutants. Furthermore, alterations in DNT-2 or Toll-2 expression levels impaired connectivity of L1 neurons at the M1 medulla layer and altered dendritic morphology of L1 neurons. These data suggest that L1 neurons could take up DNT-2 secreted from medulla neurons during the establishment of connectivity patterns. As DNT-3 (spz-3) and DNT-2 (spz-5) are expressed in the medulla and they could influence both lamina and medulla neurons, this suggests that their function maintaining cell survival could enable the stabilisation or alignment of connected neurons across medulla columns.

developmental biology↗

bioRxiv2025

Stochastic splicing and deterministic inclusion of exon variables promote diversification of Down Syndrome Cell Adhesion Molecule expression

Mutually alternative splicing in Down Syndrome Cell Adhesion Molecule (Dscam) gene of arthropods generates extraordinary molecular diversity producing tens of thousands of isoforms. From three clusters of variable exons directing homophilic interactions, one single exon is selected. Homophilic repulsion of identical isoforms directs branching of axons running in neuronal tracts, and of dendrites for generation of overlapping dendritic fields through selection of different variants in neighbouring cells. Here, we investigate the spatial inclusion of Dscam alternative exons in Drosophila and honey bees using reporter genes and in situ hybridizations, respectively. In Drosophila, we find that Dscam variable clusters 4 and 9 splicing is not always productive in reporters, resulting in suppressed expression in optic lobes and variable expression across identical cells in salivary glands and photoreceptor fields. However, in photoreceptor neurons in larvae, we find repetitive inclusion of specific variants suggesting that stochastic expression is generated at the level of splicing of the variable cluster, but inclusion of variants follows a deterministic path. Likewise, we find in larval brains, inclusion of exon 4 and 9 variants in compartmentalised and repetitive patterns. In foraging honey bees, inclusion of exon 4 and 10 variants occurs in compartmentalised patterns differing between mushroom body lobes and individuals. This indicates that initial equal inclusion of exon variants is directed to compartmentalised inclusion through experience. These findings detail a new model of experience directed alternative splicing in Dscam incorporating stochasticity through splicing productivity and deterministic selection of individual isoforms.

molecular biology↗

bioRxiv2025

Assessing species-specific neonicotinoid toxicity using cross-species chimeric nicotinic acetylcholine receptors in a Drosophila model

Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels and the main mediators of synaptic neurotransmission in the insect brain. In insects, nAChRs are pivotal for sensory processing, cognition and motor control, and are the primary target of neonicotinoid insecticides. Neonicotinoids are potent neurotoxins and pollinators such as honey bees are more sensitive and affected by extremely low sub-lethal doses. The pentameric nAChR channel is made up either of five -subunits constituting five ligand-binding sites or a mixture of two to three and {beta} subunits constitute two to three ligand-binding sites. Of particular note, the honey bee nAChR8 subunit is converted into a {beta} subunit (nAChR{beta}2) in Drosophila, raising the question whether this to {beta} conversion makes flies less sensitive to neonicotinoids. To investigate species-specific aspects of neonicotinoid toxicity we CRISPR-Cas9 engineered a cross-species chimeric nAChR subunit by swapping the ligand-binding domain in Drosophila of nAChR{beta}2 with honey bee nAChR8. Toxicity assessment by neonicotinoid thiamethoxam revealed significantly impaired motor functions in climbing and flight assays when comparing the 8/{beta}2 chimeric channel to wild type or a {beta}2 knock-out. However, both the 8/{beta}2 chimeric channel and the {beta}2 knock-out showed the same increased survival after neonicotinoid exposure compared to wild type flies. Combinatorial exposure to neonicotinoids also did not reveal differences. These findings highlight the critical role of nAChR subunit composition in motor control and demonstrate how subtle structural differences can profoundly impact motor function and pesticide response, offering new insights into the molecular mechanisms of neurotoxicity across species.

molecular biology↗